Digestive health centre

Kidney stones: Symptoms, treatment and prevention

What are kidney stones?

Kidney stones are created when certain substances in your urine, including calcium, oxalate and sometimes uric acid, crystallise. These crystals may then join together and form a kidney stone.

Kidney stones usually form within the kidney, where urine is produced before flowing into the ureter (the tube that leads to the bladder). Small kidney stones are often able to pass out of your body in your urine and may go completely unnoticed by you. But larger stones irritate and stretch the ureter as they move towards the bladder, sometimes blocking the flow of urine and typically causing excruciating pain. Sometimes, a stone can be too large to pass into the ureter and remains lodged in the kidney.

Why some people form kidney stones and others don't is not always clear. Kidney stone disease is more common in young and middle-aged adults than in the elderly. It is also more prevalent in men than women. In the UK, kidney stones affect about three in 20 men and one in 20 women.

The NHS suggests that a high-protein, low- fibrediet, inactivity, family history, some intestinal conditions and certain drug treatments (such as aspirin) can increase the risk of kidney stones forming.

The NHS also classifies risk factors according to the type of kidney stone:

People living in hot climates are sometimes more prone to kidney stones because they may become dehydrated more easily. Dehydration concentrates the minerals (and other chemicals) in the urine and makes crystal formation easier. Medical evidence suggests that drinking too little fluid can exacerbate this chemical over-saturation of the urine.

Most kidney stones are composed of calcium oxalate crystals, a kind of salt in the urine that's hard to dissolve. Uric acid, the chemical associated with gout, may also be involved. If your urine is chronically infected with certain organisms, you may be prone to getting kidney stones of a specific composition as well.

Certain people are frequent "stone formers". A person who has one stone has about a 50% chance of developing another stone over 10 years, with about a 15% risk in the first year or so.

What are the symptoms of kidney stones?

The symptoms of kidney stones include:

Waves of sharp pain that start in your back and side, and move towards the groin or testicles.

Inability to find a comfortable position, people with kidney stones often pace up and down.

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